By Deborah Inkpen
Bringing diamonds to the earth’s surface is the job
of kimberlites. Kimberlites are a peculiar kind of volcanic
rock that originate deep within the earth’s mantle
and are brought to the surface at really high speeds. Unlike
a typical volcano, kimberlites emerge violently at the surface,
producing a pipe-like structure, and don’t leave a
volcanic edifice.

“Kimberlites are full of volatiles,
and are very explosive,” explained Dr. Derek Wilton.
Dr. Wilton and Dr. Paul Sylvester, geology professors in
the Department of Earth Sciences, have been doing research
in northern Labrador on kimberlites. Dr. Wilton likens the
eruption of kimberlites to a high-speed elevator.

“Kimberlites punch their way up through the earth’s
crust and as they come up to the surface they pick up all
sorts of fragments, including diamonds,” said Dr.
Wilton. “Diamonds only form very deep at the base
of the crust and we never see them on the surface in the
rocks in which they formed. Kimberlites are the movers of
the diamonds from the lower crust to the surface. Not all
kimberlites contain diamonds, however, and you have to examine
them closely to determine if they are diamondiferous.”

The rocks that Wilton/Sylvester team are looking at are
from the Torngat Mountains, Saglek and the Makkovik areas
of Labrador. The Torngat ones are similar to those found
on the nearby Ungava Peninsula of Quebec which have been
confirmed to contain diamonds. For diamonds to form in the
mantle, Dr. Wilton explained that the land like that of
Labrador has to have mantle-friendly roots, meaning that
the land has to have been there for a long time without
a lot of movement.

“You look for diamonds on really ancient continents
and northern Labrador has got some of the oldest rocks in
the world,” he said. “We have been able to date
some rocks from Labrador at 3.9 billion years old which
is phenomenal when you realize that the earth is only four-and-a-half
billion years old.”

Part of their study is evaluating the diamond potential
of the Labrador examples. Master’s student Glen Penny
from Holyrood has been investigating whether the kimberlites
are diamond-bearing. “The other exciting thing about
kimberlites is that not only do they bring up diamonds but
they bring up other things from down in the mantle, so by
examining them, we can actually can tell something about
what the mantle is like underneath Labrador,” said
Dr. Wilton.

Based on earlier work by former postdoctoral fellow Dr.
Richard Cox, Mr. Penney is also developing a technique to
date a mineral which appears in kimberlites called perovskite.

“It’s an unusual mineral because
you only find in kimberlites or meteorites,” explained
Dr. Wilton. “We have been working on a means of dating
it in our department by using the LAM-ICP-MS (or laser ablation
microprobe-inductively coupled plasma- mass spectrometer)
instrument.

“Because diamonds seem only to have formed before
two-and-a-half billion years ago while kimberlites can be
as young as 50-million years,” said Wilton. If we
can date individual kimberlites then we can say whether
they are related to ones that we know are diamond bearing.
The technique has a potential application for diamond exploration
and some are suggesting that Canada may become the largest
diamond producer in the world in the next 10 to 15 years.”